SUNRPC: Don't display zero scope IDs

A zero scope ID means that it wasn't set, so we don't need to append
it to presentation format addresses.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

net/sunrpc/addr.c

@@ -73,6 +73,8 @@ static size_t rpc_ntop6(const struct sockaddr *sap,
 
 	if (!(ipv6_addr_type(&sin6->sin6_addr) & IPV6_ADDR_LINKLOCAL))
 		return len;
+	if (sin6->sin6_scope_id == 0)
+		return len;
 
 	rc = snprintf(scopebuf, sizeof(scopebuf), "%c%u",
 			IPV6_SCOPE_DELIMITER, sin6->sin6_scope_id);